A process and device for direct cooling breathing gas and liquid nitrogen in an intrinsically safe storage tank area

Abstract

The present application discloses a process and device for direct cooling of breathing gas from liquid nitrogen in an intrinsically safe storage tank area. The process is as follows: a jet pump is used as the power transmission equipment for the breathing gas, the breathing gas in the tank area first enters a precooler, condenses to remove some organic matter, then enters the jet pump, and contacts and exchanges heat with the low-temperature circulating recovery liquid in the jet pump. After the temperature is further reduced, it enters the condensation freezer, where it is mixed with the liquid nitrogen directly sprayed in and cooled. The organic matter in the breathing gas is condensed and frozen. The breathing gas after preliminary condensation and freezing treatment enters the precooler and serves as a cold source to exchange heat with the breathing gas in the tank area, so that the breathing gas from the tank area is cooled and precooled, and then reheated before entering the adsorption system for further purification. The present application utilizes the vaporization cold energy of liquid nitrogen to remove organic matter from the breathing gas in the storage tank area, so that it meets environmental emission requirements and has high heat transfer efficiency. At the same time, it recycles and reuses the nitrogen in the breathing gas, reducing the storage and transportation costs of hazardous chemicals.

Description

Technical Field

[0001] The present invention relates to the field of waste gas treatment, and in particular to a process and device for treating respiratory gas in a storage tank area. Background Art

[0002] Chemical tank farms store a wide variety of chemicals, resulting in complex exhaust gas compositions and placing high explosion-proof requirements on gas-powered conveying equipment. Exhaust gas levels fluctuate, and concentrations fluctuate widely, complicating the selection of gas-powered conveying equipment. Traditional condensation and refrigeration technologies often utilize partition-type cooling systems, resulting in low heat exchange efficiency. Consequently, it is necessary to design a set of breathing gas treatment equipment and processes that can adapt to these diverse operating conditions and ensure the intrinsic safety of the tank farm. Summary of the Invention

[0003] In view of the above problems existing in the prior art, the purpose of the present invention is to provide an intrinsically safe liquid nitrogen direct cooling process for breathing gas in storage tank areas, which is used to solve the difficulties encountered in the treatment of breathing gas in storage tank areas.

[0004] The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling device comprises a precooler, a jet pump, a condenser freezer, a recovery liquid temporary storage tank and a recovery liquid pump. The recovery liquid temporary storage tank contains low-temperature recovery liquid. The liquid outlet of the recovery liquid temporary storage tank is connected to the liquid inlet of the jet pump by a pipeline through the recovery liquid pump. The liquid injection port of the jet pump is further connected to the liquid inlet of the recovery liquid temporary storage tank by a pipeline, forming a circulation loop of the low-temperature recovery liquid. The precooler is a heat exchanger structure, which can be selected from a shell and tube heat exchanger, a plate heat exchanger, a spiral plate heat exchanger or a wound tube heat exchanger. The hot channel inlet of the precooler is connected to the breathing air of the storage tank area, and the hot channel outlet of the precooler is connected to the breathing air inlet of the jet pump through a pipeline. The breathing air outlet of the jet pump is then connected to the condenser freezer by a pipeline. A nozzle for spraying liquid nitrogen is also provided on the top of the condenser freezer; the air outlet of the condenser freezer is then connected to the cold channel inlet of the precooler through a pipeline, and the cold channel outlet of the precooler discharges the purified breathing air mixed with nitrogen; wherein, the liquid condensed in the hot channel of the precooler and the liquid condensed in the condenser freezer both flow into the recovery liquid temporary storage tank.

[0005] Furthermore, the condensing freezer can be selected from a shell and tube heat exchanger, a plate heat exchanger, a hollow container or a container filled with fillers.

[0006] The device of the present application also includes an adsorption post-treatment system, which includes a reheater and an adsorption system. The cold channel outlet of the precooler is connected to the reheater and the adsorption system in sequence through a pipeline; the adsorption system includes a single-stage or multi-stage adsorption tower connected in parallel, and the adsorption tower is filled with an adsorbent for adsorbing organic matter, and the adsorbent includes at least one of activated carbon, molecular sieve, zeolite and adsorption resin.

[0007] Furthermore, the device of the present application also includes a nitrogen heater, a high-pressure nitrogen buffer tank and a low-pressure buffer tank. The air outlet of the adsorption system is connected to the high-pressure nitrogen buffer tank and the low-pressure buffer tank in sequence through pipelines; the air outlet of the high-pressure nitrogen buffer tank is also connected to the nitrogen heater through a bronchial tube, and the nitrogen heater is then connected to the low-pressure buffer tank through a pipeline through a condensing freezer to form a flow path for the thawed gas.

[0008] The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling process comprises the following steps:

[0009] 1) Breathing gas transportation: The low-temperature recovered liquid in the recovery liquid temporary storage tank serves as the jet circulating liquid for the jet pump. The jet pump serves as the power transmission equipment for the breathing gas. The jet pump circulates the low-temperature recovered liquid to draw in and eject it, creating a negative pressure at the jet pump's breathing gas inlet and sucking the precooler's hot channel. The breathing gas in the storage tank area is pre-cooled in the precooler's hot channel and then continuously drawn into the jet pump (after entering the jet pump, the breathing gas comes into contact with the low-temperature circulating recovered liquid in the jet pump for heat exchange, further reducing its temperature). After being ejected by the jet pump, it enters the next condensation and freezing process.

[0010] The cold fluid entering the cold channel of the precooler is the initially purified breathing air discharged from the condenser freezer, and the liquid condensed in the hot channel of the precooler flows into the recovery liquid temporary storage tank for temporary storage;

[0011] 2) Condensation and freezing of breathing gas: After being ejected by the jet pump, the breathing gas enters the condenser freezer and mixes with the injected liquid nitrogen. The liquid nitrogen vaporizes in the condenser freezer, absorbing a large amount of heat energy to lower the temperature of the breathing gas. The organic matter in the breathing gas is condensed into liquid in the condenser freezer and flows into the recovery liquid temporary storage tank or frozen and attached to the inner wall of the condenser freezer, thereby removing most of the organic matter in the breathing gas. The preliminarily purified breathing gas mixed with nitrogen is discharged from the condenser freezer.

[0012] 3) Thawing: After the solids frozen on the inner wall of the condenser freezer in step 2 have accumulated to a certain amount, the thawing step is performed. A portion of the breathing gas from the mixed nitrogen in the high-pressure nitrogen buffer tank is heated to a certain temperature by a nitrogen heater and then enters the condenser freezer as thawing gas, melting the solids attached to the inner wall of the condenser freezer into liquid, which flows into the recovery liquid temporary storage tank. The cooled thawing gas enters the buffering process;

[0013] 4) Breathing gas adsorption: After initial purification by recovering cold energy in step 1), the breathing gas is reheated in a reheater and then enters the adsorption system for further treatment, allowing organic matter in the breathing gas to be adsorbed on the adsorbent, thereby achieving the purpose of completely purifying the breathing gas. The completely purified breathing gas then enters the buffering process;

[0014] 5) Cache of purified gas: The completely purified breathing gas in step 4) enters the high-pressure nitrogen cache tank, part of which is used as the thawing gas in step 3), and the rest enters the low-pressure cache tank. The thawed gas after passing through the condenser freezer in step 3) directly enters the low-pressure cache tank. The cached gas is used as nitrogen sealing gas for storage tanks, hazardous chemical vehicles and hazardous chemical ships.

[0015] 6) Transfer of recovered liquid: The liquid generated in steps 1), 2) and 3) is temporarily stored in the recovered liquid temporary storage tank and pumped into the jet pump as circulating liquid. At the same time, the recovered liquid exceeding the liquid level is transported to a safe place by the recovered liquid pump.

[0016] Furthermore, in step 1), the breathing gas in the storage tank farm is composed of the following components by volume: less than 65% organic gas, with the remainder being nitrogen; the volume concentration of the organic gas in the breathing gas is preferably 5-65%. The saturated vapor pressure of the organic gas at 20°C is ≥ 2 kPa.

[0017] Furthermore, in step 1), the initial temperature of the breathing gas is room temperature, and the intake flow rate of the breathing gas is 800 Nm 3 / h or less, preferably 50~800Nm 3 / h, the temperature of the pre-cooled breathing air coming out of the pre-cooler is -5~15℃.

[0018] Furthermore, the temperature of the low-temperature recovery liquid entering the jet pump is -25~-80°C, and the temperature of the breathing gas coming out of the jet pump is -40~-5°C; the temperature of the breathing gas after the preliminary purification of the mixed nitrogen gas discharged from the condenser freezer is -30~-150°C, preferably -50~-150°C, and the organic matter content in the breathing gas after the preliminary purification of the mixed nitrogen gas is less than 200mg / m 3 , the removal rate of organic matter reaches more than 95%.

[0019] Furthermore, the temperature of the gas coming out of the reheater is 0~-15℃, and the organic matter content in the breath gas coming out of the adsorption system is less than 60mg / m 3 , preferably 10 mg / m 3 the following.

[0020] Furthermore, in step 3), the temperature of the gas coming out of the nitrogen heater is 60-120°C.

[0021] Furthermore, the adsorption system in step 4) can be set or deleted according to actual needs.

[0022] The beneficial effects achieved by this application are:

[0023] 1. The breathing gas treatment process in the breathing gas liquid nitrogen direct cooling process in the intrinsically safe storage tank area of ​​this application adopts a jet pump as the system's conveying power, instead of using dynamic equipment such as fans as the power conveying equipment for the breathing gas, so that the entire breathing gas treatment system is inherently safe.

[0024] 2. In the liquid nitrogen direct cooling process for breathing gas in the intrinsically safe storage tank area of ​​this application, liquid nitrogen is directly sprayed in the condensing freezer. The sprayed liquid nitrogen is in direct contact with the breathing gas for heat exchange. The tiny droplets of liquid nitrogen can quickly vaporize and absorb heat to quickly cool the breathing gas. The heat transfer efficiency is high, which greatly improves the utilization rate of cold energy. A good condensing and freezing technical effect can be achieved by using a condensing freezer with a smaller heat exchange area.

[0025] 3. The liquid nitrogen direct cooling process for breathing gas in the intrinsically safe storage tank area of ​​this application can achieve ultra-low emissions of breathing gas in the tank area.

[0026] 4. The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling process of this application recycles the nitrogen sealing gas in the storage tank as nitrogen sealing gas for storage tanks, hazardous chemical vehicles and hazardous chemical ships, thereby improving the safety of the unloading process.

[0027] This application utilizes the vaporization cold energy of liquid nitrogen to remove organic matter from breathing air in storage tank areas, ensuring compliance with environmental emission requirements. It also recycles and reuses the nitrogen in the breathing air, reducing the storage and transportation costs of hazardous chemicals. Furthermore, the direct contact of liquid nitrogen with the breathing air enhances heat transfer efficiency and improves condensation and freezing efficiency. Furthermore, the system utilizes a jet pump as its power system, eliminating the need for fans or other powered equipment to deliver the breathing air, significantly improving the safety of breathing air delivery in storage tank areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of the breathing gas liquid nitrogen direct cooling device in the storage tank area of ​​this application;

[0029] Figure 1 Middle: 1-precooler, 2-jet pump, 3-condenser freezer, 4-recovery liquid temporary storage tank, 5-adsorption system, 6-high-pressure nitrogen buffer tank, 7-low-pressure nitrogen buffer tank, 8-nitrogen heater, 9-recovery liquid pump, 10-nitrogen reheater. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0031] Example: Control Figure 1

[0032] The liquid nitrogen direct cooling device for breathing gas in the storage tank area includes a precooler 1 for precooling breathing gas, a jet pump 2 for conveying breathing gas, a condensation freezer 3 for condensing and freezing organic matter in the breathing gas, a condensate temporary storage tank 4 for temporarily storing condensate, an adsorption system 5 for deeply removing organic matter from the breathing gas, a high-pressure nitrogen buffer tank 6 for caching high-pressure purified gas, a low-pressure nitrogen buffer tank 7 for caching low-pressure purified gas, a nitrogen heater 8 for heating thawed gas, a recovery liquid pump 9 for conveying recovery liquid, and a nitrogen reheater 10 for reheating the preliminarily purified breathing gas.

[0033] comparison Figure 1 The breathing gas discharge port of the storage tank is connected to the hot channel inlet of the precooler 1 by a pipeline, the hot channel outlet of the precooler 1 is connected to the gas inlet of the jet pump 2 by a pipeline, and the liquid condensed in the hot channel of the precooler 1 is transported to the condensate temporary storage tank 4 through a pipeline. The cold channel outlet of the precooler 1 is connected to the air inlet of the nitrogen reheater 10 by a pipeline, the air outlet of the nitrogen reheater 10 is connected to the adsorption system 5 by a pipeline, the gas outlet of the jet pump 2 is connected to the breathing gas inlet of the condenser freezer 3 by a pipeline, and a nozzle for spraying liquid nitrogen is also provided on the top of the condenser freezer 3, the liquid outlet of the jet pump 2 is connected to the liquid inlet of the condensate temporary storage tank 4 by a pipeline, the breathing gas outlet of the condenser freezer 3 is connected to the cold channel inlet of the precooler 1 by a pipeline, and the liquid outlet of the condenser freezer 3 is connected to the condensate temporary storage tank 4 by a pipeline. The liquid inlet is connected by a pipeline, the thawed gas outlet of the condenser freezer 3 is connected to the inlet of the low-pressure nitrogen buffer tank 7 by a pipeline, the air outlet of the adsorption system 5 is connected to the inlet of the high-pressure nitrogen buffer tank 6 by a pipeline, the outlet of the high-pressure nitrogen buffer tank 6 is connected to the inlet of the low-pressure nitrogen buffer tank 7 by a pipeline, the outlet of the low-pressure nitrogen buffer tank 7 is connected to each gas-using unit by a pipeline, the liquid outlet of the condensate temporary storage tank 4 is connected to the inlet of the recovery liquid pump 9 by a pipeline, one outlet of the recovery liquid pump 9 is connected to the jet pump 2 by a pipeline, and the other outlet is connected to the outside of the boundary by a pipeline.

[0034] The breathing gas in the tank area first passes through the preheater 1 to reduce its temperature and condense a small amount of organic matter into the condensate temporary storage tank 4. The pre-cooled breathing gas is transported to the condenser freezer 3 through the jet pump 2. In the condenser freezer 3, it is mixed with the sprayed liquid nitrogen. The liquid nitrogen vaporizes and absorbs a large amount of heat energy, which reduces the temperature of the breathing gas. Most of the organic matter in the breathing gas is separated and preliminarily purified. After the preliminary purification of the mixed nitrogen, the breathing gas enters the cold channel of the precooler 1 as the cold source of the precooler 1, and then enters the adsorption system 5 after being reheated by the nitrogen reheater 10 to be completely purified. The completely purified breathing gas enters the high-pressure nitrogen buffer tank 6. The high-pressure nitrogen A portion of the purified gas in the gas buffer tank 6 is used as thawing gas. It is first heated to a certain temperature by a nitrogen heater and then goes to the condenser freezer 3. The organic matter attached to the inner wall of the condenser freezer 3 is melted into liquid and flows into the condensate storage tank 4. The cooled thawing gas enters the low-pressure nitrogen buffer tank 7. Another portion of the purified gas in the high-pressure nitrogen buffer tank 6 flows into the low-pressure nitrogen buffer tank 7. The nitrogen in the low-pressure nitrogen buffer tank 7 is finally used as nitrogen sealing gas for storage tanks, hazardous chemical vehicles and hazardous chemical ships. The low-temperature recovery liquid in the condensate storage tank 4 is used as the circulating liquid of the jet pump 2. The recovery liquid exceeding the liquid level is pumped to a safe place through the recovery liquid pump 9.

[0035] The precooler 1 is a heat exchanger structure, which can be selected from a shell and tube heat exchanger, a plate heat exchanger, a spiral plate heat exchanger or a wound tube heat exchanger. The condenser freezer 3 can be selected from a shell and tube heat exchanger, a plate heat exchanger, a hollow container or a container filled with filler. The condenser freezer 3 can preferably be a hollow container or a container filled with filler. The nozzle is arranged in the top of the condenser freezer 3, an air inlet is arranged at the bottom of the condenser freezer 3, an air outlet is arranged at the top of the condenser freezer 3, a defoamer is arranged in the air outlet, and a liquid outlet valve is arranged at the bottom of the condenser freezer 3 and connected to the recovery liquid temporary storage tank 4 through a pipeline, so that the liquid condensed in the condenser freezer 3 flows into the recovery liquid temporary storage tank 4. The adsorption system 5 includes a single-stage or multi-stage adsorption tower connected in parallel, and the adsorption tower is filled with an adsorbent for adsorbing organic matter. The adsorbent includes at least one of activated carbon, molecular sieve, zeolite and various adsorption resins.

[0036] Example 1:

[0037] Use Figure 1 The device shown in the figure takes the breathing gas from an acetone storage tank as an example, and performs a liquid nitrogen direct cooling process for the breathing gas, including the following steps:

[0038] 1) Breathing gas delivery: The breathing gas in the acetone storage tank is composed of the following components by volume: 70% nitrogen and 30% acetone. The inlet temperature of the breathing gas in the acetone storage tank is 25°C and the inlet flow rate is 100m 3 / h. Driven by the jet pump, the breathing air first passes through the hot channel of the precooler and is cooled to -5°C. The condensed acetone flows into the condensate storage tank. The -5°C breathing air from the hot channel of the precooler is cooled to -25°C by the jet pump before entering the condenser freezer.

[0039] The preliminary purified breathing gas from the condenser freezer at -112℃ is heated to -27℃ after passing through the cold channel of the precooler, and is then heated to 5℃ after passing through the reheater before entering the adsorption system.

[0040] 2) Condensation and freezing of breathing gas: The condensation freezer uses a hollow container (the container volume is about 1m 3 , using a double elliptical head container, external dimensions: DN1000mmX1200mm), a nozzle for spraying liquid nitrogen is set on the top of the hollow container (liquid nitrogen spray flow rate is 160kg / h, temperature is -170℃), the -25℃ breathing gas is mixed with the 160kg / h sprayed liquid nitrogen in the condenser freezer and cooled, and the acetone breathing gas after preliminary purification of the mixed nitrogen is discharged from the condenser freezer, and its outlet temperature drops to -112℃.

[0041] Most of the acetone is condensed or solidified in the condenser freezer, and the liquid acetone flows into the condensate temporary storage tank. The acetone temperature in the temporary storage tank is -45℃, and the solidified solid acetone adheres to the inner wall of the condenser freezer. After condensation and freezing, the acetone content in the mixed nitrogen breathing gas is reduced to 40mg / m 3 The recovery rate of acetone in the condenser freezer reaches 99.98%. The initially purified acetone breathing gas is heated to 5°C after passing through the precooler and reheater and then enters the adsorption system.

[0042] 3) Thawing: Step 2) When the acetone solids adhering to the inner wall of the condenser freezer have accumulated to a certain amount, thaw them and take 50m3 of the high-pressure nitrogen buffer tank. 3 / h of purified gas is used as thawing gas, which is heated to 80℃ by a nitrogen heater and then enters the condenser freezer to melt the acetone solid attached to the inner wall of the condenser freezer into liquid and flows into the recovery liquid temporary storage tank. After the temperature is cooled to 20℃, the thawing gas enters the low-pressure nitrogen buffer tank;

[0043] 4) Adsorption of respiratory gas: After the initial purification of respiratory gas after condensation, freezing and rewarming to 5°C in step 2, it enters the adsorption system for further organic matter removal (the adsorption system uses activated carbon as the adsorbent), further removing 80% of the acetone in the respiratory gas, reducing the acetone content in the respiratory gas to 10mg / m 3 Below, then enter the high-pressure nitrogen buffer tank;

[0044] 5) Purified gas buffering: The completely purified breathing gas from step 4) enters the high-pressure nitrogen buffer tank, part of the purified gas is used as the thawing gas for step 3), and the remaining purified gas enters the low-pressure buffer tank. The thawed gas at 20°C after passing through the condenser freezer in step 3) directly enters the low-pressure buffer tank. The buffered gas is used as nitrogen sealing gas for storage tanks, hazardous chemical vehicles, and hazardous chemical ships.

[0045] 6) Transfer of recovery liquid: The liquid produced in steps 1), 2) and 3) is temporarily stored in the recovery liquid temporary storage tank and used as the circulating liquid of the jet pump. Acetone exceeding the liquid level is transported to a safe place by the recovery liquid pump.

[0046] As described in step 2) of Example 1, if a partitioning heat exchanger is used to replace the condensing freezer for partitioning heat exchange, 160 kg / h of liquid nitrogen is also introduced as the cold fluid into the cold channel of the partitioning heat exchanger, and the acetone-containing tail gas is introduced into the hot channel of the partitioning heat exchanger for heat exchange. If the acetone-containing tail gas is also cooled to -112°C, the heat exchange area of ​​the partitioning heat exchanger needs to reach 20 m 2 , the cost is based on 1m 3 More than 3 times that of a hollow container.

[0047] The present invention treats the complex breathing gas in the storage tank area to ultra-low emissions while recycling the nitrogen blanketing gas in the storage tank, reducing storage and transportation costs. In addition, the entire system adopts an intrinsically safe design and does not contain gas conveying equipment such as fans that are prone to sparks, greatly improving the safety of breathing gas delivery in the storage tank area.

[0048] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments.

Claims

1. A process for direct cooling of breathing gas in liquid nitrogen in an intrinsically safe storage tank area, characterized in that The following steps are involved: 1) Breathing gas delivery: The low-temperature recovered liquid in the recovery liquid temporary storage tank is used as the jet circulation liquid of the jet pump. The jet pump (2) serves as the power delivery equipment for the breathing gas. The jet pump circulates the low-temperature recovered liquid and ejects it to form a negative pressure at the breathing gas inlet of the jet pump, and sucks the hot channel of the precooler. The breathing gas in the storage tank area is precooled in the hot channel of the precooler and continuously sucked into the jet pump. After being ejected by the jet pump, it enters the next condensation and freezing process. The cold fluid introduced into the cold channel of the precooler (1) is the initially purified breathing gas discharged from the condenser freezer (3), and the liquid condensed in the hot channel of the precooler flows into the recovery liquid temporary storage tank for temporary storage; 2) Condensation and freezing of breathing gas: After being ejected by the jet pump, the breathing gas enters the condenser freezer and mixes with the injected liquid nitrogen. The liquid nitrogen vaporizes in the condenser freezer, absorbing a large amount of heat energy to lower the temperature of the breathing gas. The organic matter in the breathing gas is condensed into liquid in the condenser freezer and flows into the recovery liquid temporary storage tank or frozen and attached to the inner wall of the condenser freezer, thereby removing most of the organic matter in the breathing gas. The preliminarily purified breathing gas mixed with nitrogen is discharged from the condenser freezer. 3) Thawing: After the solids frozen on the inner wall of the condenser freezer in step 2 have accumulated to a certain amount, the thawing step is performed. A portion of the breathing gas from the mixed nitrogen in the high-pressure nitrogen buffer tank is heated to a certain temperature by a nitrogen heater and then enters the condenser freezer as thawing gas, melting the solids attached to the inner wall of the condenser freezer into liquid, which flows into the recovery liquid temporary storage tank. The cooled thawing gas enters the buffering process; 4) Adsorption of respiratory gas: After the initial purification by recovering cold energy in step 1), the respiratory gas is reheated in the reheater and then enters the adsorption system (5) for further treatment, so that the organic matter in the respiratory gas is adsorbed on the adsorbent, thereby achieving the purpose of completely purifying the respiratory gas. The completely purified respiratory gas then enters the buffering process; 5) Purified gas buffering: The completely purified breathing gas from step 4) enters a high-pressure nitrogen buffer tank, with a portion used as thawing gas for step 3), and the remainder enters a low-pressure buffer tank. The thawed gas from step 3) that passes through the condenser freezer enters the low-pressure buffer tank directly. The buffered gas is used as nitrogen blanketing gas for storage tanks, hazardous chemical vehicles, and hazardous chemical vessels. 6) Transfer of recovered liquid: The liquid generated in steps 1), 2) and 3) is temporarily stored in the recovered liquid temporary storage tank and pumped into the jet pump as circulating liquid. At the same time, the recovered liquid exceeding the liquid level is transported to a safe place by the recovered liquid pump.

2. The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling process according to claim 1 is characterized in that In step 1), the breathing gas in the storage tank area is composed of the following components in volume fractions: less than 65% of organic gas and the rest is nitrogen.

3. The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling process as claimed in claim 2, characterized in that In step 1), the volume concentration of organic matter in the breathing gas in the storage tank area is 5-65%; the saturated vapor pressure of the organic matter at 20° C. is ≥2 kPa.

4. The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling process according to claim 1 is characterized in that In step 1), the initial temperature of the breathing gas is room temperature, and the intake flow rate of the breathing gas is 50~800Nm 3 / h, the temperature of the pre-cooled breathing air coming out of the pre-cooler (1) is -5~15℃; The temperature of the low-temperature recovery liquid entering the jet pump (2) is -25~-80℃, and the temperature of the breathing gas coming out of the jet pump (2) is -40~-5℃; the temperature of the breathing gas after the initial purification of the mixed nitrogen discharged from the condenser freezer (3) is -30~-150℃, and the organic matter content in the breathing gas after the initial purification of the mixed nitrogen is less than 200mg / m 3 , the organic matter removal rate is over 95%.

5. The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling process as claimed in claim 4, characterized in that The temperature of the initially purified breathing gas of the mixed nitrogen discharged from the condenser freezer (3) is -50 to -150°C.

6. The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling process as claimed in claim 2, characterized in that The temperature of the gas coming out of the reheater is 0~-15℃, and the organic matter content in the breath gas coming out of the adsorption system (5) is less than 60mg / m 3 .

7. The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling process according to claim 6, characterized in that The organic matter content in the breath gas from the adsorption system (5) is 10 mg / m 3 the following.

8. An intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling device, characterized in that The invention comprises a precooler (1), a jet pump (2), a condenser freezer (3), a recovery liquid temporary storage tank (4) and a recovery liquid pump (9), wherein the recovery liquid temporary storage tank (4) contains low-temperature recovery liquid, the liquid outlet of the recovery liquid temporary storage tank (4) is connected to the liquid inlet of the jet pump (2) by a pipeline through the recovery liquid pump (9), and the liquid injection port of the jet pump (2) is further connected to the liquid inlet of the recovery liquid temporary storage tank (4) by a pipeline, thereby forming a circulation loop of the low-temperature recovery liquid; The nitrogen heater (8), the high-pressure nitrogen buffer tank (6) and the low-pressure nitrogen buffer tank (7), the gas outlet of the adsorption system (5) are connected to the high-pressure nitrogen buffer tank (6) and the low-pressure nitrogen buffer tank (7) in sequence through pipelines; the gas outlet of the high-pressure nitrogen buffer tank (6) is also connected to the nitrogen heater (8) through a bronchial tube, and the nitrogen heater (8) is further connected to the low-pressure nitrogen buffer tank (7) through a pipeline via a condenser freezer (3), forming a flow path for the thawed gas; The precooler (1) is a heat exchanger structure selected from a shell and tube heat exchanger, a plate heat exchanger, a spiral plate heat exchanger or a wound tube heat exchanger. The hot channel inlet of the precooler (1) is connected to the breathing air of the storage tank area. The hot channel outlet of the precooler (1) is connected to the breathing air inlet of the jet pump (2) through a pipeline. The breathing air outlet of the jet pump (2) is further connected to the condenser freezer (3) through a pipeline. A nozzle for spraying liquid nitrogen is also provided on the top of the condenser freezer (3); The condenser freezer (3) is selected from a shell and tube heat exchanger, a plate heat exchanger, a hollow container or a container filled with fillers, and the gas outlet of the condenser freezer (3) is connected to the cold channel inlet of the precooler (1) through a pipeline, and the cold channel outlet of the precooler (1) discharges the purified breathing gas mixed with nitrogen; The liquid condensed in the hot channel of the precooler (1) and the liquid condensed in the condenser freezer (3) both flow into the recovery liquid temporary storage tank (4).

9. The intrinsically safe storage tank area breathing gas liquid nitrogen direct cooling device according to claim 8, characterized in that It also includes an adsorption post-treatment system, the adsorption post-treatment system including a reheater (10) and an adsorption system (5), and the cold channel outlet of the precooler (1) is connected to the reheater (10) and the adsorption system (5) in sequence through pipelines; The adsorption system (5) comprises a single-stage or multi-stage adsorption tower connected in parallel, wherein the adsorption tower is filled with an adsorbent for adsorbing organic matter, and the adsorbent comprises at least one of activated carbon, molecular sieve, zeolite and adsorption resin.

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